He was born in São Paulo, Brazil, in 1917. He settled in Greece in 1925, where he remained until 1945, returning in 2000 after a career spanning Europe and America, where he lived until his death in 2007.
In 1932, he began working in a furniture workshop while simultaneously studying furniture design for two years at the Vocational Night School. There, his painting teacher, Tzeni Manousi, encouraged him to pursue sculpture and painting. Shortly after, he worked for Varangis -as a furniture maker-, and in 1940 for the painter N. Nikolaou.
Although he pursued independent studies in painting, he was taught the technique of woodcutting by T. Kanthos. In 1945, on a scholarship from the French government, he studied for three months at the École des Arts Décoratifs under Marcel Gimond and A.-Au. Janniot. From 1947 to 1953, he worked as a model maker for the architect Le Corbusier. During the same period, he began exhibiting at the Salon d’Automne in Paris, where he became a member and, in 1982, its president. In Paris, he came into contact with contemporary artistic movements and turned to the use of metal and the technique of welded brass.
His multifaceted body of work—encompassing painting, sculpture, engraving, set design, and costume design (for theater and opera)—was presented in 80 solo exhibitions (in Greece, France, Switzerland, Belgium, Germany, and Brazil) and 150 group exhibitions worldwide. He participated in the Biennials of Antwerp (1953), the Netherlands (1956), Painting and Sculpture for Young Artists (Paris, 1957), Printmaking (Ljubljana, 1963), Venice (1966), and Sculpture (Italy, 1975), as well as the French Sculpture Triennial (Paris, 1978 and 1995) and the Panathenaea of Sculpture (Athens, 1965).
He was honored by the French state with the Legion of Honour, the title of Commandeur of the Order of Arts and Letters, and the title of Officier of Arts and Letters. In 1988, he was awarded the Antoine Pevsner International Sculpture Prize. He established the non-profit ‘Costas Andreou Foundation’ with the aim of promoting his work and supporting young artists through awards.